Abstract: Obliterative bronchiolitis (OB) is the leading cause of late death after lung transplantation (LTx) and the principle unmet obstacle to improved long-term outcomes. Increasing evidence indicates a role for recipient autoimmunity in the pathogenesis of graft rejection. Emphysema, a principle indication for LTx, has been shown to express a wide-spectrum of extracellular matrix autoreactive antibodies and T cells directed towards collagen, elastin, and decorin, the impact of which on post-Tx outcomes is unknown. Here we will utilize mouse models of emphysema, and orthopic LTx, to investigate LTx outcomes in a clinically relevant scenario. The scientific premise of these studies is to determine if pre-transplant autoreactive immunity induced by emphysema, promotes post-Tx injury that leads to exacerbated ischemia reperfusion injury (IRI) and OB. The earliest injury to the LTx occurs as a consequence of IRI, the severity of which is thought to lead to accelerated onset OB. Ischemic insult followed by reperfusion leads to the exposure of neoepitopes expressed on stressed/injured cells recognized by natural self-reactive IgM Abs, which bind and activate the C system, resulting in inflammation and injury. We have identified annexin IV as an injury-specific neoepitope expressed in ischemic transplant grafts, and have shown that this neoepitope binds natural IgM, activates C and promotes IRI. By means of an anti-annexin IV single chain Ab (B4scFv), we have validated annexin IV as a target for the therapeutic delivery of C inhibition to murine allografts. There are a number of therapeutic benefits of this neoepitope targeting approach for protection against IRI in a LTx recipient: 1. It will target the proximal event in complement activation, 2. The targeting vehicle itself contributes to therapeutic activity by blocking the binding of complement activating antibodies, and 3. Will inhibit C activation locally, which will impair T cell activation. Our working hypothesis is that pre-transplant autoreactivity to extracellular matrix targets exacerbates early graft injury, thus promoting early onset OB. We propose that neoepitope IgM graft-targeted C inhibitors will synergize to inhibit adaptive autoantibody effector functions, and reduce intragraft autoreactive T cell activity. We propose the following specific, independent, but interrelated aims. 1. Determine the complement-mediated effector functions that contribute to extracellular matrix autoreactive immunity induced acute lung graft injury. Here we will determine the isotype and phenotype of autoreactive antibodies and T cells that promote injury post transplantation and further dissect the complement effector functions that induce graft damage, and 2. In a murine model of OB, determine whether cigarette smoke-induced autoimmunity exacerbates IRI and chronic rejection following transplantation in a complement-dependent manner. We will transplant lungs into emphysematous mice (induced by cigarett...